1. Field of the Invention
The present invention relates to a microprocessor having a waiting function, and more particularly, a microprocessor which is arranged to keep an address given to a read-only memory (ROM) for storing micro-instructions unchanged with respect to a given period of time in order to realize the waiting function.
2. Description of the Related Art
As a starting point, the inventors of the present invention used a commonly available microprocessor which was arranged to transit its internal state on a basis of a predetermined system clock for processing the data. When the microprocessor reads data from an external storage unit or a peripheral unit having a slow operating ratio, the system clock is stopped for blocking the transit of the state inside of the microprocessor as is required, thereby enabling a timing delay for data entry. In this state, apparently, the microprocessor is temporarily stopped.
However, the foregoing microprocessor is often kept waiting for a considerably long time, when the system clock remains inoperative. Therefore, in the case that a dynamic circuit is used in the microprocessor, the electric potential charged in the internal signal line is discharged, that is, made lower, resulting in disadvantageously changing the internal state of the microprocessor.
This disadvantage may be overcome if the microprocessor is composed of a static circuit. However, utilizing the static circuit makes a scale (size) of the circuit larger. This is another disadvantage.